U.S. patent number 4,552,571 [Application Number 06/596,892] was granted by the patent office on 1985-11-12 for oxygen generator with two compressor stages.
This patent grant is currently assigned to VBM Corporation. Invention is credited to Fernand J. Dechene.
United States Patent |
4,552,571 |
Dechene |
November 12, 1985 |
Oxygen generator with two compressor stages
Abstract
A first compressor (10) supplies atmospheric air or other
gaseous mixtures to a crossover valve (20) at a first relatively
low pressure, e.g., 15-18 psi. The crossover valve alternately
supplies the atmospheric air to a first molecular sieve bed (22)
and a second molecular sieve bed (24) while simultaneously
permitting the other molecular sieve bed to discharge adsorbed
gaseous components of atmospheric air through a waste gas discharge
port (26). A second compressor (40) draws the oxygen which passes
through the molecular sieve beds without being adsorbed through a
restrictor (60) and a needle valve (62). The restrictor and needle
valve are selected and adjusted such that an oxygen pressure of
about 2-6 psi is maintained upstream of at least the needle valve.
The second compressor increases the pressure of the oxygen to at
least 45 psi and pumps it into a storage tank (46) from which it
may be supplied to welding or other industrial equipment.
Inventors: |
Dechene; Fernand J. (New
Britain, CT) |
Assignee: |
VBM Corporation (Louisville,
KY)
|
Family
ID: |
24389160 |
Appl.
No.: |
06/596,892 |
Filed: |
April 5, 1984 |
Current U.S.
Class: |
95/22; 95/130;
95/96; 96/113; 96/130 |
Current CPC
Class: |
B01D
53/04 (20130101); B01D 53/0446 (20130101); Y02C
20/10 (20130101); B01D 2257/102 (20130101); B01D
2257/402 (20130101); B01D 2256/12 (20130101) |
Current International
Class: |
B01D
53/04 (20060101); B01D 053/04 () |
Field of
Search: |
;55/23-26,31,33,35,58,59,62,68,74,75,161-163,179,180,316,387,389 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Spitzer; Robert
Attorney, Agent or Firm: Fay, Sharpe, Fagan, Minnich &
McKee
Claims
Having thus described a preferred embodiment of the invention, the
invention is now claimed to be:
1. A method of separating a primary product gas from a gaseous
mixture, the method comprising:
supplying the gaseous mixture at a first relatively low pressure
alternately to first and second molecular sieve beds which each
contain a physical separation medium which selectively adsorbs at
least one adsorbable component of the mixture and passes the
primary product gas and causing the adsorbable component to be
removed from the other of the first and second beds;
drawing the primary product gas from adjacent the molecular sieve
beds to increase a pressure drop thereacross such that the primary
product gas has a second relatively low pressure adjacent the
molecular sieve beds;
limiting the second relatively low pressure to positive
pressures;
selectively adjusting a rate at which primary product gas is drawn
from the molecular sieve beds to adjust the purity thereof;
increasing the pressure of the primary product gas from the second
relatively low pressure to a relatively high pressure;
storing the increased pressure primary product gas in a storage
tank; and,
maintaining the storage tank generally at the relatively high
pressure.
2. The method as set forth in claim 1 wherein the second relatively
low pressure is about 2-6 psi and the relatively high pressure is
at least 45 psi.
3. The method as set forth in claim 2 wherein the first relatively
low pressure is about 15-18 psi.
4. The method as set forth in claim 1 further including regulating
the flow rate and pressure of the primary product gas from the
molecular sieve bed before the primary product gas is increased in
pressure to the relatively high pressure.
5. The method as set forth in claim 1 further including the step of
monitoring the storage pressure in the storage tank and selectively
controlling the pressure increasing step to maintain the storage
pressure in the storage tank substantially constant.
6. A method of separating oxygen from atmospheric air, the method
comprising:
supplying the air at a first relatively low pressure alternately to
one of first and second molecular sieve beds which contain a
physical separation medium that selectively adsorbs nitrogen and
other components of air and passes through oxygen, while causing
the nitrogen and other adsorbable components to be removed from the
other of the first and second beds, oxygen rich gas being
discharged from an oxygen outlet of the molecular sieve beds;
selectively drawing air through a compressor as the compressor is
started;
after the compressor is started, drawing the oxygen rich gas from
the molecular sieve bed oxygen outlet through the compressor to
reduce the pressure at the molecular sieve bed oxygen outlet and to
increase oxygen rich gas pressure to a relatively high
pressure.
7. The method as set forth in claim 6 wherein the relatively high
pressure oxygen rich gas is supplied to a storage tank and further
including selectively starting and stopping a second compressor to
maintain the oxygen rich gas in the storage tank generally at the
relatively high pressure.
8. An apparatus for supplying a primary product gas at a relatively
high pressure, the apparatus comprising:
a first compressor means for providing a gaseous mixture at a first
relatively low pressure;
a valving means for alternately channelling the gaseous mixture
from the first compressor means alternately to a first end of each
of at least two molecular sieve beds for separating the primary
product gas from the gaseous mixture;
a second compressor means which receives the primary product gas
from a second end of the molecular sieve beds for maintaining
pressure adjacent the second end of the molecular sieve beds at a
second relatively low pressure which is less than the first
relatively low pressure and for supplying the primary product gas
to a primary product outlet at a relatively high pressure which
relatively high pressure is greater than both the first and second
relatively low pressures; and,
a second compressor start-up valve means for selectively (a)
enabling the second compressor to be operated without load for a
start-up duration and (b) after the start-up duration, channelling
the primary product gas from the sieve beds through the second
compressor means to downstream equipment, the start-up valve means
being operatively connected with the sieve beds second end and the
second compressor means, whereby the second compressor means is
able to be started without load.
9. The apparatus as set forth in claim 8 further including a flow
and pressure regulating means disposed between the molecular sieve
bed second ends and the second compressor means for regulating the
flow rate of the primary product gas to the second compressor means
and for regulating the amount that the second compressor means
draws down the second relatively low pressure.
10. The apparatus as set forth in claim 9 wherein the pressure and
flow regulating means includes a pressure and flow regulator
restrictor means for restricting the flow of the primary product
therethrough and causing a pressure drop thereacross and an
adjustable valve means for selectively adjusting the flow of the
primary product gas therethrough and adjusting the primary product
pressure upstream thereof.
11. The apparatus as set forth in claim 10 further including a pair
of restrictor means connected in parallel with each other and each
connected in series between the pressure and flow regulator
restrictor means and the second end of one of the molecular sieve
beds.
12. The apparatus as set forth in claim 9 further including welding
equipment connected downstream from the second compressor
means.
13. An apparatus for supplying oxygen rich gas at a relatively high
pressure to downstream welding equipment and the like, the
apparatus comprising:
at least two molecular sieve beds for separating an oxygen rich gas
from a gaseous mixture, the molecular sieve beds having air inlets
at a first end thereof and oxygen outlets at a second end
thereof;
a first compressor means for providing air at a first, positive
pressure;
a valving means for alternately channelling the air from the first
compressor means to one of the sieve bed air inlets and for
connecting another of the molecular sieve bed air inlets with a
waste gas outlet;
a second compressor means operatively connected with the molecular
sieve bed oxygen outlets for drawing the oxygen rich gas to a
second, relatively low pressure which is less than the first
positive pressure;
a flow and pressure regulating means operatively between the
molecular sieve bed oxygen outlets and the second compressor means
for selectively regulating the flow rate and pressure of oxygen
rich gas flowing from the molecular sieve bed oxygen outlets such
that the second pressure is maintained positive, whereby the flow
and pressure regulating means and the second compressor means
interact to bring the pressure at the molecular sieve bed second
ends to a low but positive second pressure; and,
an oxygen storage tank operatively connected downstream from the
second compressor means to receive compressed oxygen rich gas
therefrom at a third pressure, which third pressure is greater than
both the first and second pressures, the oxygen supply tank being
adapted for interconnection with the downstream welding
equipment.
14. The apparatus as set forth in claim 13 wherein the flow and
pressure regulating means includes an adjustable flow control means
for selectively (a) increasing the rate of oxygen rich gas flow
through the flow and pressure regulating means while decreasing a
concentration of oxygen therein and (b) decreasing the oxygen rich
gas flow rate while increasing the concentration of oxygen therein,
whereby the flow rate and purity of oxygen to the oxygen reservoir
is selectively adjustable.
15. The apparatus as set forth in claim 13 wherein the first
pressure is less than 45 psi, the second pressure is about 2-6 psi
and the third pressure is at least 45 psi.
16. The apparatus as set forth in claim 13 further including a
start up valve means associated with the second compressor means
for enabling the second compressor to be actuated without load.
17. The apparatus as set forth in claim 13 further including a
pressure sensitive control means for controlling the second
compressor means in response to the pressure in the storage tank
such that a generally constant pressure is maintained therein.
18. The apparatus as set forth in claim 17 further including second
compressor start up valve means operatively connected with the
pressure sensing means for enabling the second compressor means to
be actuated without load for a preselected duration and after the
preselected duration for connecting the second compressor means in
series between the pressure and flow regulating means and the
storage tank.
19. The apparatus as set forth in claim 18 wherein the first
compressor means is interconnected with a power supply such that
the first compressor means runs continuously while the pressure
sensing means switches the second compressor means on and off.
20. An apparatus for supplying an oxygen rich gas at a relatively
high pressure to downstream welding equipment, the apparatus
comprising:
a first compressor means for providing air at a first pressure;
a valving means for alternately channelling the air from the first
compressor means alternately to a first end of each of at least two
molecular sieve beds for separating oxygen rich gas from the
air;
a second compressor means which receives the oxygen rich gas from a
second end of the molecular sieve beds and supplies the oxygen rich
gas to a storage tank at a selected, relatively high pressure;
pressure sensing means for sensing oxygen rich gas pressure in the
storage tank; and,
a control operatively connected to the first compressor means, the
second compressor means, and the pressure sensing means, the
control causing (1) the first compressor means to run substantially
continuously and (2) the second compressor means to run
intermittently, as necessary to maintain said selected relatively
high pressure in the storage tank.
Description
BACKGROUND OF THE INVENTION
The present invention pertains to the art of molecular separation,
specifically the physical separation or fractionating of molecular
components of a gaseous mixtures. The invention finds particular
application in the separation of oxygen from the other components
of atmospheric air to supply oxygen to welding equipment and will
be described with particular reference thereto. It is to be
appreciated, however, that the present invention is also applicable
to the separation of other gaseous mixtures and is particularly
applicable to applications in which the segregated gases are to be
supplied at relatively high pressures.
Heretofore, components have been separated or fractionated from
gaseous mixtures utilizing a method and apparatus generally as
described in U.S. Pat. No. 2,944,627, issued July 12, 1960 to
Charles W. Skarstrom. The Skarstrom system pressurized the gaseous
mixture to be fractionated with a compressor or the like. A
crossover valving assembly channelled the pressurized gaseous
mixture alternately to first and second vessels containing a
molecular separation material. The crossover valving assembly
further connected the vessel which was not receiving the gaseous
mixture with a waste gas or secondary product discharge port. The
molecular separation material selectively adsorbed one or more
components of the gas and passed one or more other components
connoted as a primary product gas. The primary product gas which
passed through the vessel was channelled in part to a primary
product outlet and in part to the other vessel. The primary product
gas portion channelled to the other vessel flushed the adsorbed or
secondary product gases therefrom out the secondary product
discharge port. Cyclically, the crossover valving assembly switched
the connection of the vessels with the incoming gaseous mixture and
the secondary product discharge port. This cyclic switching of the
vessels provided a continuing, though cyclically surging, flow of
the primary product gas. Because the flow rate of the primary
product gas varied at different portions of the cyclic switching
cycle, a surge tank was commonly connected with the outlet so that
a relatively even product flow would be provided by the
apparatus.
For welding and other industrial operations, oxygen is supplied at
45 psi or better. In order to maintain a 45 psi pressure in the
surge tank and compensate for a pressure drop across the vessels,
the input compressor was required to supply the gaseous mixture to
the vessels at about 65 psi. To produce oxygen at an average rate
of 10 cubic feet per hour required about a one horsepower
compressor. Higher oxygen supply rates required correspondingly
higher horsepower compressors.
One of the drawbacks of the prior art oxygen generators for
supplying oxygen to welding equipment was the relatively large
amount of electrical or other energy consumed by the compressor.
Another drawback was that the amount and pressure of output oxygen
varied or surged during the production system as the vessels were
switched. Yet another drawback was that the compressor was required
to supply gas at about 65 psi to maintain about 45 psi in the surge
tank.
The present invention contemplates a new and improved gas
fractioning apparatus and method which provides primary product
more efficiently, at a higher pressure, and with less energy
consumption.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an
apparatus for fractioning components of a gaseous mixture. A first
or input compressor means provides a supply of the mixture to be
fractionated at a first relatively low pressure, e.g., 15-18 psi. A
valving means alternately channels the gaseous mixture from the
first compressor means to an input end of at least first and second
beds. The beds each contain a physical separation medium which
adsorbs at least one adsorbable component of the mixture and passes
at least one substantially nonadsorbable component or primary
product gas. The beds are connected at an output end thereof with a
second or booster compressor means which boosts the pressure of the
primary product gas from a second relatively low pressure, e.g.,
2-6 psi, adjacent its inlet to a relatively high pressure, e.g., 65
psi.
In accordance with another aspect of the present invention, there
is provided a method of fractioning components of a gaseous
mixture. The gaseous mixture is supplied at a first relatively low
pressure alternately to at least two beds containing a physical
separation medium which adsorbs at least one adsorbable component
and passes at least one substantially nonadsorbable component or
primary product gas. The pressure of the primary product gas
downstream from the beds is maintained at a second relatively low
pressure, e.g., 2-6 psi, and boosted to a relatively high pressure,
e.g., 65 psi, at a primary product gas outlet.
One advantage of the present invention is that it produces the
primary product gas more efficiently. Particularly, the back
pressure at the primary product outlet end of the beds is
maintained relatively low and relatively constant. This produces a
relatively flat output flow rate of the primary product gas from
the beds which, in turn, produces more useable product.
Another advantage of the present invention is that it provides a
substantial power savings. The total horsepower consumed by the two
compressors is about half the horsepower required by the input
compressors of the prior art. For example, a one-third horsepower
input compressor and a one-fifth horsepower booster compressor have
been found to produce about 81/2 cubic feet per hour. As is to be
appreciated, this is about half the one horsepower required in the
above-described prior art apparatus to produce ten cubic feet per
hour of comparably pure oxygen.
Another advantage of the present invention is that it enables
larger amounts of oxygen to be stored. The present invention
enables oxygen to be stored at 65 psi or even 100 psi or more.
Under these higher pressures substantially more oxygen can be
stored in the same size storage tank than at the 45 psi as commonly
stored prior art units.
Still further advantages of the present invention will become
apparent upon reading and understanding the following detailed
description of the preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may take form in various steps and arrangements of
steps and in various parts and arrangements of parts. The drawings
are only for purposes of illustrating a preferred embodiment to the
invention and are not to be construed as limiting it.
FIG. 1 is a block diagram of an apparatus in accordance with the
present invention for separating a primary product gas from a
gaseous mixture; and,
FIG. 2 is a diagrammatic illustration of an electrical control
circuit for the apparatus of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to FIG. 1, a first or input compressor means A
supplies a gaseous mixture, such as atmospheric air, at a first
relatively low pressure, to a molecular sieve bed assembly B. The
molecular sieve bed assembly separates a primary product gas, such
as oxygen, from the gaseous maixture. A second or boster compressor
means C draws the primary product gas from the molecular sieve bed
assembly B and boosts its pressure to a relatively high pressure.
The relatively high pressure primary product gas is supplied to a
primary product outlet which is adapted to be interconnected with
welding equipment D or the like. A flow and pressure regulating
means E regulates the flow rate and pressure of the primary product
gas between the molecular sieve bed assembly and the booster
compressor means to maintain optimum primary product production
conditions. By adjusting the pressure and flow rates, the
production rate and the purity of the primary product are
selectively adjustable. A control circuit F controls the operation
and cycling of the first compressor means, the molecular sieve bed
assembly, the second compressor means, and other components.
The first compressor means A includes a compressor, such as a
carbon vane compressor, 10 which compresses atmospheric air or
another received gaseous mixture to a first relatively low
pressure, in the preferred embodiment, about 15-18 psi. However,
other pressures below 45 psi are also contemplated. A check valve
12 assures a unidirectional gaseous mixture flow from the first
compressor 10 to a filter 14. The filter removes contaminants such
as carbon dust, oil vapors, and the like from the gaseous mixture.
A heat exchanger 16 conserves energy by cooling the gaseous mixture
with a waste or secondary product gas as it expands into the
atmosphere.
The molecular sieve bed assembly B includes a crossover valving
means 20 which alternately directs the pressurized gaseous mixture
to a first bed 22 and a second bed 24, while connecting the bed
which is not receiving the gaseous mixture to a waste gas outlet
port 26. In the preferred embodiment, the beds are filled with a
physical separation medium or material which selectively adsorbs
one or more adsorbable components or secondary product gases and
passes one or more nonadsorbable components or primary product
gases of the gaseous mixture. The physical separation material is a
molecular sieve with pores of uniform size and essentially the same
molecular dimensions. These pores selectively adsorb molecules in
accordance with molecular shape, polarity, degree of saturation,
and the like. In the preferred embodiment, the physical separation
material is a zeolite which has pores of the appropriate dimension
to adsorb nitrogen, carbon monoxide, carbon dioxide, water vapor,
and other significant component of air, but not oxygen which is
passed as the primary product gas rather than being adsorbed. Type
5A and type 13X zeolite have been found satisfactory.
The crossover valving means 20 under the control of the control
circuit F alternates cyclically between a first position and a
second position. In the first position, the gaseous mixture is
channelled into the first bed first end. Primary product gas is
discharged from the first bed second end through a first restrictor
means 28. A portion of the primary product gas is channelled
through a second restrictor means 30 into the second bed second
end. The adsorbed secondary product gases are flushed from the
second bed first end, through the crossover valve 20, and out the
waste gas outlet port 26. Another portion of the primary product
gas is channelled through a third restrictor means 32.
In the second crossover valve position, the gaseous mixture is
channelled to the second bed first end. Primary product gas is
discharged from the second bed second end through the second
restrictor means 30. A portion of the primary product gas is
channelled through the first restrictor means 28 to flush the
adsorbed second product gases from the first bed. Another portion
of the primary product gas is discharged through the third
restrictor means 32.
The third restrictor means 32 is connected with the primary product
output of the molecular sieve bed assembly B. The restrictiveness
of the third restrictor means 32 relative to the first and second
restrictor means 28, 30 determines the relative portion of the
primary product gas which is returned to flush the bed being
regenerated. A check valve 34 assures that the primary product gas
is only discharged from the molecular sieve bed assembly B and that
atmospheric air or other gases are not drawn in.
The pressure booster means C includes a second compressor means 40
such as a diaphragm type compressor. It is contemplated, that other
types of compressors which are suitable for pumping and compressing
about 95 percent pure oxygen gas may also be utilized. Compressor
start up valving means 42, 44 enable the second compressor means 40
to be started free of load. After the second compressor means is
started, the start up valving means are actuated to the position
shown in FIG. 1 such that a primary product gas is drawn from the
molecular sieve bed assembly B and supplied to a storage tank 46 at
a relatively high pressure, 45 psi or more with 65 psi or more
being preferred. However, it is contemplated that primary product
gas may be stored at a lower pressure if the downstream equipment D
can be operated at such lower pressures. As described in greater
detail in conjunction with FIG. 2, a pressure sensing switch means
48 selectively actuates and deactuates the second compressor means
40 in order to maintain a preselected storage pressure in the
storage tank 46. A check valve 50 assures that the primary product
gas is received by the storage tank 46 but not discharged therefrom
through the compressor start up valving means 42. An on-off primary
product control switch 52 selectively enables and disables primary
product gas to flow from the storage tank 46 to a primary product
outlet 54. A check valve 56 assures that propane, acetylene, or
other welding gases are not allowed to enter the primary product
storage tank 46.
The flow and pressure control means E prevents the second
compressor means 40 from drawing a vacuum on the first and second
sieve beds. The second vacuum pump maintains relatively low,
positive pressure at the primary product output end of the sieve
beds. In the preferred embodiment, the pressure at the primary
product output end of the beds is several pounds lower than the
pressure supplied to the inlet end. This pressure differential
reduces the amount of work required of the first compressor to move
or pump the gas through the molecular sieve beds. Thus, the present
invention permits the first compressor to have a lower horsepower
because the sieve beds operate at a lower pressure.
The flow and pressure regulating means E include a fourth
restrictor 60 to reduce the output pressure of the sieve bed
assembly B still further. The fourth restrictor smooths the primary
product flow rate and pressure from the sieve bed assembly
sufficiently that no surge tank is required. In the preferred
embodiment, the fourth restrictor means 60 in conjunction with the
first, second and third restrictor means reduces the output primary
product pressure to about zero psi. A flow control valve means,
such as a needle valve 62, throttles back the flow of primary
product therethrough such that the primary product pressure is
maintained at 2 to 6 psi upstream thereof during operation of the
second compressor. In the preferred embodiment, the needle valve is
adjusted such that the flow rate therethrough matches an optimum
primary product output flow rate for the sieve bed assembly. That
is, at different flow rates, the sieve bed assembly produces oxygen
of different purities. The flow rate through the needle valve is
adjusted to select the best available flow rate for the selected
purity. Increasing the flow rate permitted by the needle valve
tends to provide a greater volume of primary product gas but with a
lower oxygen concentration; decreasing the flow rate through the
needle valve tends to provide a smaller volume of primary product
gas but with a higher concentration of oxygen.
With reference to FIG. 2, the control circuit F includes an on-off
switch 70 connected with the nongrounded side of a 120 volt or 240
volt power supply. The first compressor 10 is connected in series
with the on-off switch and power supply such that it runs
continuously whenever the unit is actuated by the on-off switch 70.
A cooling fan motor 72 is likewise connected in parallel with the
first compressor such that it too runs continuously whenever the
unit is on. A mechanical timer motor 74 is connected in parallel
with the first compressor means for cyclically opening and closing
a time controlled switch 76. The time controlled switch 76 is
connected in series with the crossover valve 20 for cyclically
moving the crossover valve between its first and second positions
with a regular periodicity. The second compressor 40 is connected
in series with the pressure sensing switch means 48 such that the
second compressor 40 is actuated and responds to the pressure
sensing switch sensing a pressure below the preselected storage
pressure, e.g., below 65 psi. A time delay relay 78 is connected in
parallel with the second compressor and in series with the pressure
sensing switch for closing a relay means 80 a preselected duration
after the pressure sensing switch is actuated, e.g., five seconds.
The relay means 80 is connected in series with the compressor start
up valves 42 and 44. In this manner, the compressor start up valves
42 and 44 move from a nonactuated position in which the second
compressor operated under no load to the actuated position
illustrated in FIG. 1 in which the second compressor draws the
primary product from the pressure and flow regulator means E and
pumps it to the storage tank 46.
The invention has been described with particular reference to the
preferred embodiment. Various alterations and modifications will
become apparent upon reading and understanding the preceding
detailed description of the preferred embodiment. It is intended
that the invention be construed as including all such alterations
and modifications insofar as they come within the scope of the
appended claims or the equivalents thereof.
* * * * *